Specifically, should the rail system diverge from I-5 to connect workers to the state’s largest manufacturing center, even if it means higher costs? Or would it be better to follow a more direct path along I-5 to downtown Everett, which might not attract as many riders?

“Those two options kind of become the arm-wrestling match,” Snohomish County public works director Steve Thomsen said.

As it stands, arguments in favor of a Paine Field route appear to be prevailing. During a Sound Transit presentation to the Snohomish County Council on Tuesday, some council members suggested they would support an option designed to serve the tens of thousands of aerospace workers at Paine Field. The city of Everett also strongly favors that option.

Another possibility, other than light rail, would be starting up a rapid-transit bus line to Paine Field, similar to Community Transit’s SWIFT bus on Highway 99.

Whatever happens will take years to materialize.

Planning for a Lynnwood-to-Everett rail leg is underway now to prepare for a possible ballot measure in 2016. If the Sound Transit Board decides to ask voters to raise tax dollars for more light-rail expansion, they must present a preferred route with an estimated price tag.

“We can’t go after funding for aspects of a transportation system if we don’t have the planning work ahead of it,” said Everett City Councilman Paul Roberts, who serves on the Sound Transit Board. “This is really opening the door to pursue those dollars.”

As part of that effort, the agency has come up with five draft plans. Three involve three possible light rail routes and two others rapid-transit bus routes.

“It’s a very high-level view of what’s possible,” said Patrice Hardy, a Sound Transit government-affairs liaison.

Early plans envision a Lynnwood-to-Everett line passing through Paine Field that would stretch over 15.7 miles and cost up to $3.4 billion to build. Traveling that distance would take 33 minutes. Planners predict that 37,000 to 50,000 riders would use it daily.

A direct Lynnwood-to-Everett connection along I-5 would cover 12.6 miles and cost up to $2.2 billion. Fewer daily riders — an estimated 32,000 to 43,000 — would be likely to use it.

A middle option, in terms of cost and distance, would follow I-5 north to 128th Street, then cut west to Highway 99. Its estimated daily ridership of up to 51,000 is similar to the Paine Field route.

Those plans all stop in downtown Everett. The city supports extending the line another two miles to Everett Community College and Providence Regional Medical Center Everett, spokeswoman Meghan Pembroke said.

As an alternative to rail, there are two proposals for rapid bus lines. The more expensive is projected to cost up to $740 million. While significantly cheaper than light rail, buses are only projected to attract half as many riders, if that.

No timeline is attached to the future expansion.

The Boeing Co. has acknowledged parking constraints at Paine Field as a problem for its approximately 40,000 Everett-based employees. The company has maxed out 21,000 permitted parking spaces.

Boeing and Everett are studying the issue and considering alternatives to more on-site parking.

Light-rail or rapid-bus connections might help — some day.

“If they can’t add employees because they don’t have places for those employees to park, they’re going to take those jobs somewhere else,” airport director Dave Waggoner said. “If we can reduce the need to use land for surface parking by having a better transportation system, then we encourage people to provide jobs here.”

The issue isn’t just about Boeing, Waggoner added, but also about other aerospace companies such as Aviation Technical Services, which employees about 1,000.

Foreign executives who tour Paine Field are sometimes mystified at the lack of mass-transit options for bringing people to jobs at the airport.

“What surprises these people are all of these cars in the parking lot,” said John Monroe, chief operating officer for Economic Alliance Snohomish County. “Where’s your rapid transit? Where’s your light rail system to bring all of these people to work?”

Off the drawing board, real construction work is underway to expand Sound Transit’s light rail system. Along I-5 in north Seattle, drivers can see crews building the section from the University District to Northgate. That leg is on track to finish by 2021.

Sound Transit has committed to building the line to Lynnwood by 2023. The agency still has to finish acquiring the right of way, spokesman Bruce Gray said.

Separately, Sound Transit is studying land between I-5 and 52nd Avenue West in Lynnwood as a possible site for a future maintenance yard. Lynnwood opposes the plan. Sound Transit also is eying locations for the yard in Bellevue.

Noah Haglund: 425-339-3465; nhaglund@heraldnet.com.

Public hearing

Sound Transit has scheduled an open house and public hearing on its long-range plans and related environmental studies.